Solid-state yeast fermentation optimizes properties of hard wheat bran.

Eating foods rich in bran became somewhat of a health craze about two decades ago with the massive promotion of bran cereals and granola. In the late 1980s, oat products in all shapes and sizes flooded the market, claiming to lower blood cholesterol levels and fight heart disease. This craze peaked around 1990 and was short-lived, as studies showed that oat bran only modestly reduced cholesterol levels. However, in January 1997, the FDA determined that food containing a certain amount of oat bran or rolled oats can carry a label claiming that the product may reduce the risk of heart disease, when it is combined with a low-fat diet.

Scientists at the University of Maryland evaluated the potential of a solid-state yeast fermentation system to improve the health-promoting properties of wheat bran, including its extractable antioxidant properties, protein content, and soluble and insoluble fiber composition. They indicate that a solid-state yeast treatment may be a commercially viable post-harvest approach to improving the health-promoting properties of wheat bran and other wheat-based food ingredients.

Three commercially available food grade yeasts were evaluated. The researchers examined the impact of yeast dosage and treatment time, as well as how these factors would affect the health-promoting properties of wheat bran. The investigators found that a solid-state yeast treatment was able to significantly enhance releasable antioxidant properties such as the scavenging capacities against peroxyl (ORAC); 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) cation; 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radicals; total phenolic content (TPC); and phenolic acids.

The researchers also showed that a commercial food-grade yeast significantly changed the fiber content of wheat bran, and all yeasts experienced up to a 12% increase in their protein content. In addition, both the ORAC and TPC of wheat bran were altered by the amount of yeast dosage, treatment time and their subsequent interactions.

Further information. Dr. Liangli (Lucy) Yu, Associate Professor, Department of Nutrition and Food Science, University of Maryland, 0112 Skinner Building, College Park, MD 20742; phone: 301-405-0761; fax: 301-314-3313; email: lyu5@umd.edu.